How to change background color of selected RecyclerView item in Kotlin

In this android kotlin source code example, we are going to change background color of selected RecyclerView item in Kotlin.

You can copy and adopt this source code example to your Kotlin android project without reinventing the wheel.

Below is a step by step source code to change background color of selected RecyclerView item in Kotlin.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".recyclerView.RecyclerViewActivity20">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.kt

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.recyclerview.widget.RecyclerView
import com.bluapp.kotlinview.R
import androidx.recyclerview.widget.DividerItemDecoration
import androidx.recyclerview.widget.LinearLayoutManager
import android.widget.TextView
import android.widget.RelativeLayout
import android.view.LayoutInflater
import android.view.ViewGroup
import android.content.Context
import android.graphics.Color
import android.view.View


class RecyclerViewActivity20 : AppCompatActivity() {
    private var list: RecyclerView? = null
    private var recyclerAdapter: adapter? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_recycler_view20)
        list = findViewById(R.id.list) as RecyclerView
        val country = arrayListOf<String>()
        country.add("Nigeria")
        country.add("China")
        country.add("USA")
        country.add("Ghana")
        country.add("Canada")
        country.add("Finland")
        country.add("Denmark")
        country.add("Argentina")
        country.add("Andorra")
        country.add("Togo")
        val layoutManager = LinearLayoutManager(this)
        list!!.setLayoutManager(layoutManager)
        recyclerAdapter = adapter(this@RecyclerViewActivity20, country)
        list!!.addItemDecoration(DividerItemDecoration(list!!.getContext(), layoutManager.orientation))
        list!!.setAdapter(recyclerAdapter)
    }

    private inner class adapter(internal var context: Context, internal var mData: List<String>) :
        RecyclerView.Adapter<adapter.myViewHolder>() {
        internal var index = -1

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): adapter.myViewHolder {
            val view =
                LayoutInflater.from(context).inflate(R.layout.recyclerview_adapter20, parent, false)
            return myViewHolder(view)
        }

        override fun onBindViewHolder(holder: adapter.myViewHolder, position: Int) {
            holder.country.text = mData[position]
            holder.relativeLayout.setOnClickListener {
                index = position
                notifyDataSetChanged()
            }

            if (index == position) {
                holder.relativeLayout.setBackgroundColor(Color.parseColor("#FF4081"))
                holder.country.setTextColor(Color.parseColor("#FFFFFF"))
            } else {
                holder.relativeLayout.setBackgroundColor(Color.parseColor("#FFFFFF"))
                holder.country.setTextColor(Color.parseColor("#000000"))
            }
        }

        override fun getItemCount(): Int {
            return mData.size
        }

        inner class myViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
            internal var relativeLayout: RelativeLayout
            internal var country: TextView

            init {
                relativeLayout = itemView.findViewById(R.id.relativeLayout)
                country = itemView.findViewById(R.id.country)
            }
        }
    }

}

recyclerview_adapter20.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relativeLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <TextView
        android:id="@+id/country"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_marginTop="10dp"
        android:layout_margin="10dp"
        android:text="Country"
        android:textColor="#000000"
        android:textSize="18sp"
        android:textStyle="bold" />

</RelativeLayout>

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